The present invention relates to a transition arrangement between a waveguide and microstrip wherein a substrate supporting a microstrip conductor on one side and a ground plane on an opposite side penetrates into the waveguide which has a short-circuited end. A portion of the microstrip conductor carried by the substrate penetrates into the interior of the waveguide to couple in the waveguide modes. The microstrip conductor is brought into the interior of the waveguide through a channel made in the waveguide wall. A waveguide-microstrip transition of this type is described in German Pat. No. 2,421,795.
A characteristic problem in such transitions is the quality of the contact that the ground plane of the substrate carrying the microstrip conductor makes with the waveguide, because the broadband characteristics and insertion loss of the transition depend decisively upon the quality of the contact of the ground plane.